1. Field of the Invention
The present invention relates to a linear motor used, for example, with industrial machine tools, semiconductor packaging equipment, and the like.
2. Description of the Related Art
A linear motor of one prior art has a stator and a mover. In the stator, permanent magnets are arranged with a predetermined pitch (pole-to-pole distance) Pm between adjacent magnets.
With the above configuration, the linear motor introduces a predetermined current corresponding to the position of the armature of the mover to the armature winding, resulting in an electromagnetic effect between the armature windings and the permanent magnets of the stator that causes the mover to move linearly along the direction of travel. While at this time magnetic imbalance then occurs at both ends of the armature core, producing a cogging thrust, the prior art offsets this cogging thrust using the auxiliary teeth by establishing a separation distance Dt between the auxiliary teeth at both end portions (a distance between the center positions in the travel direction of the auxiliary teeth) that satisfies the following equation:Dt=(2n−1)Pm/2 (where n is a natural number)
In addition, note that the cogging thrust includes a plurality of components, such as a primary component and a secondary component, there are known techniques of another prior art that work to decrease both the primary component and the secondary component with the objective of further decreasing the cogging thrust.
The primary component of the cogging thrust is a cogging component in which one wavelength included in the cogging thrust waveform is equivalent to the above pitch Pm, and the secondary component is a cogging component in which two wavelengths are equivalent to the above pitch Pm. In this prior art, the separation distance Dt between the auxiliary teeth is set within the range below, and the height Ht of the auxiliary teeth (the dimension in the direction orthogonal to the direction of travel) is set within an appropriate range less than or equal to the height Ho of the main teeth.(2n−1)Pm/8≦Dt≦(2n−1)Pm/2With this arrangement, a decrease in both the primary component and the secondary component of the cogging thrust is achieved.